Dynamo-electric machine field magnet construction with split poles



Sept 8, 1959 Filed July 22, 1957 P. E. BESSIERE 2,903,610DYNAMO-ELECTRIC MACHINE FIELD MAGNET cous'mucnou wI'rH SPLIT POLES 4Sheets-Sheet 1 wa u mnxwm ATTORNEY Sept. 8, 1959 P. E. BESSIERE IDYNAMO-ELECTRIC MACHINE FIELD MAGNET CONSTRUCTION WITH SPLIT POLES 4Sheets-Sheet 2 Filed July 22, 1957 HWENTOR mam; ET; ml; Pxssumc Sept. 8,1959 P. E. BESSIEIYQE DYNAMO-ELECTRIC MACHINE FIELD MAGNET CONSTRUCTIONwrm SPLIT POLES 4 Sheets-Sheet 3 Filed July 22, 1957 /NVEN7'0R Heme ETIENME besa :RQ

P 3, 1959 P. E. BESSIERE 2,903,610

DYNAMO-ELECTRIC MACHINE FIELD MAGNET CONSTRUCTION WITH SPLIT POLES 4Sheets-Sheet 4 Filed July 22, 1957 /NVEN TOR PHTRQE E'UENM BE SERE BY EUnited States Patent DYNAMO-ELECTRIC MACHINE FIELD MAGNET CONSTRUCTIONWITH SPLIT POLES Pierre Etienne Bessiere, Paris, France, assignor, bymesne assignments, to Societe Anonyme Etablissements Labinal, Paris,France, a society of the French Republic Application July 22, 1957,Serial No. 673,344

Claims priority, application France August 22, 1956 9 Claims. (Cl.310-254) The present invention relates to inductor devices for electricrotating machines having projecting field poles, that is to say in whichthe coils which create the inductor flux are wound around pole coresprojecting radially from a supporting framework. The invention is moreespecially concerned with devices of this kind in which every pole coreis constituted by two core elements practically insulated from eachother, from the magnetic point of view, by a non magnetic spaceextending radially over at least most of the height of the core.

The chief object of the present invention is to provide a device of thiskind which is better adapted to meet the requirements of practice, inparticular from the point of View of easy construction and assembly.

The invention consists essentially in constituting the supportingframework of such a device by a kind of rigid closed cage the bars ofwhich are made of a magnetic material, said bars being parallel to anddistributed around the axis of the cage, each bar supporting, along itslongitudinal edges, two respective core elements of opposed polarities,the intervals or gaps between said bars consisting of a non magneticmaterial (either gaseous or solid), and being respectively disposedopposite the intervals between the pairs of core elements whichconstitute the respective poles.

Preferred embodiments of this invention will be here inafter describedwith reference to the appended drawings given merely by way of exampleand in which:

Fig. 1 is a perspective view, with parts cut away, of a dynamo inductordevice made according to the invention.

Fig. 2 is a perspective view of a portion of such a device madeaccording to a modification.

Figs. 3 and 4 show respectively in cross-section on the line IIl-III ofFig. 4 and in longitudinal section on the line IVIV of Fig. 3, anothermodification of the inductor device according to the invention.

Figs. 5 to 8 are perspective views illustrating other modifications ofthis invention, respectively.

Figs. 9 to 11 are longitudinal sections of three modifications of adetail of a cage made according to Figs. 7 and 8.

Figs. 12 and 13 show, respectively in perspective views and inlongitudinal section, still another modification of the invention.

Figs. 14 and 15 show two modifications of an element of the device ofthe Figs. 12 and 13.

It will be supposed in the following description that the invention isapplied to the construction of an inductor for a dynamo or a starterhaving a high power for a given weight.

It should first be reminded that, chiefly for purposes of reducing theweight and eliminating the armature reaction, it has already beenproposed, in inductor devices having projecting poles and for use inelectrical rotating machines, to constitute each of the poles by twocore elements practically insulated from each other, from the magneticpoint of view, by a non magnetic space,

the roots of two consecutive core elements of opposed polarities beingconnected together by a magnetic piece, so that the whole of these twocore elements and of said magnetic piece forms a single unit the crosssection of which is substantially in the form of a horseshoe.

The manufacture of such units, either made of a single piece or ofseveral identical pieces juxtaposed in the longitudinal direction (caseof laminated poles), and the mounting of the inductor coils on suchunits are delicate and costly operations. Furthermore, these units mustbe accurately secured on a rigid supporting framework so that theirrelative positions are quite correct.

In order to obviate this drawback, according to the present invention,the supporting framework on which are mounted said core elements, whichare made separately, is constituted by a kind of rigid closed cage thebars of which are made of a magnetic material, said bars being parallelto and distributed around the axis of the cage, each of said barssupporting, along its longitudinal edges respectively, two core elementsof opposed polarities, the intervals or gaps between the bars, whichintervals are made of a non magnetic material (either gaseous or solid),being disposed respectively in radial alignment with the spaces betweenthe two magnetic core elements which constitute every pole.

On the drawings, reference numeral 1 designates the core elements ofeach pole, said elements being advantageously laminated, as known, andbeing manufactured separately.

These core elements are fixed directly, for instance by means of screws2, on the bars of magnetic material 3 the assembly of which forms theabove mentioned cage. Every bar 3 is in the form of a prism or cylinderhaving longitudinal generatrices, that is to say extending parallel tothe axis of the machine. The circumferential dimension of every bar isgreater than its thickness. Advantageously, as shown by the drawings,each bar 3 is in the form of an annular sector.

Two core elements 1 of opposed polarities are carried by thelongitudinal edges of every bar 3, said core elements projectingradially toward the axis of the cage. Each bar 3 is separated from theadjacent one by an interval 4 which constitutes a gap between thesebars, said gaps 4 being in radial alignment with the non mag-' neticspaces 4:: provided between the two core elements of every pole.

The provision of such a gap 4 has the following advantages:

It prevents an undesirable armature reaction flux from being closedthrough the cage, thus practically eliminating such flux,

It permits of reducing the weight of the cage.

The non magnetic material which constitutes said gaps may be eithergaseous (air for instance) or solid (stainless steel, aluminium, and soon The assembly of the bars of such an inductor is very easy. Itsufiices, for this purpose, to slip the coils 5 on the respective pairsof core elements forming the poles, and then to fix said pairs of coreelements with the coils mounted thereon on the bars 3 of the cage bymeans of screws 2.

In the construction of Fig. 1, the cage as a whole is constituted by atubular piece of a magnetic material in which are provided slots 4 whichform the air gaps (such slots being formed by milling or by cutting witha blowpipe), the bars 3 consisting of the portions of said tubular piecethat are left between said slots 4. It will be seen that the undesirablearmature reaction flux which tends to propagate in a circumferentialdirection in every pole can in the present case be formed only bypassing through the bridges 6 of magnetic material which are left at theends of air gaps 4 and which of course serve to assemble the bars 3which form the cage.

The detrimental action of these bridges is reduced, for instance byreducing their longitudinal dimensions in their middle part, as shown byFig. 2, where the ends of the air gaps are wedge-shaped.

'In order to obtain the same result, the air gaps 4 may be made of alength equal to or even greater than that of the core elements 1, asshown by Figs. 3 and 4, so that the cage extends longitudinally beyondsaid cores and even beyond coils 5. With such an arrangement, thebridges 6 are practically outside of the path which the armaturereaction flux would follow and only a negligible portion of the flux canpass through said bridges.

Another way of eliminating the armature reaction flux consists in makingbars 3 of a magnetic material and interconnecting them by bridges 7 of anon magnetic material, as shown by Fig. 5.

Said bridges 7 may be made of a metal such as stainless steel which iswelded to the mild steel which constitutes bars 3. This is thearrangement illustrated by Fig. 6.

In the construction of Fig. 6, the bridges 7 are fixed by screws to bars3.

According to another embodiment of this invention, bars 3 are directlyfixed on end discs 8 (as shown on Fig. 7) which constitute bearings forthe rotor of the machine.

These discs may be made of a non magnetic material but this is notnecessary, especially when they are provided with notches 9 (Fig. 8) inline with air gaps 4.

Bars 3 are preferably fixed to discs 8 by means of screws 10, therelative radial position of said bars with respect to said discs beingaccurately determined by suitable shoulders, as shown on Figs. 9, 10 and11.

According to another embodiment illustrated by Figs. 12 and 13, bars 3are caught in a framework 11 of a non magnetic material such asaluminium or an alloy thereof, when said framework is cast or moulded,said framework forming the gaps 4 and the bridges 7. One of the enddiscs 8 may even be constituted by a portion of said framework (Fig.13).

Said framework might even include both of the end discs 8 of the cage bymaking said framework of two portions assembled together along adiametral plane of the machine.

In order to have bars 3 securely held in framework 11, the edges of saidbars 3 may be provided with projections or lugs 12 (Fig. 14) adapted tobe caught in the non magnetic material of the framework, when the latteris cast or moulded. Notches or recesses such as 13 (Fig. 15) may also beprovided into which said non magnetic material of the frameworkpenetrates.

When the gaps 4 instead of being air gaps are constituted by a nonmagnetic solid material, the rigidity of the system is improved.

What I claim is:

1. For use in a rotating electric machine, an inductor cage including aplurality of bars'parallel to and distributed around the axis of saidcage, said bars being made of a magnetic material, the gaps between saidbars consisting of a non magnetic material, a plurality of field polesprojecting radially from said cage, each of said poles consisting of twoelongated core elements extending respectively along the respectivefacing edges of two of said bars adjacent to each other, with a nonmagnetic space between said two core elements, said spaces being in linewith said gaps, said core elements being distinct pieces rigidly securedto said magnetic bars, and a plurality of coils surrounding said fieldpoles, the two core elements forming each of said poles being surroundedby one of said coils, respectively.

2. An inductor device according to claim 1, in which said gaps betweenthe bars are air gaps.

3. An inductor device according to claim 1, in which said gaps betweenthe bars are filled with a non magnetic solid material.

4. An inductor device according to claim 1, in which said bars areportions of a tubular unit of a magnetic material provided withlongitudinal slots forming said air gaps between said bars, the portionsof said tubular unit on either sides of said slots forming magneticbridges of small dimensions.

5. An inductor device according to claim 4, in which the length of saidslots is at least equal to that of said core elements.

6. An inductor device according to claim 1, in which said bars of amagnetic material are assembled together by parts of a non magneticmaterial.

7. An inductor device according to claim 1, further including end discsat right angles to the axis of said cage for supporting and assemblingsaid bars of a magnetic material.

8. An inductor device according to claim 1, including a framework of anon magnetic material, said bars being embedded in said framework.

9. An inductor device according to claim 1 including a framework of anon magnetic material, said bars being secured in said framework by amolded construction, the edges of said bars being toothed, so as toensure a secure assembly with the framework.

References Cited in the file of this patent UNITED STATES PATENTS1,625,051 Papst Apr. 19, 1927 2,535,004 Willits Dec. 19, 1950 2,710,930Bloomenthal June 14, 1955 2,804,680 Flagg Sept. 3, 1957 FOREIGN PATENTS17,812 Great Britain of 1887 870,576 Germany Mar. 16, 1953

